Abstract

We used a sensitive method based on tetramers of peptide and major histocompatibility complex II (pMHCII) to determine whether CD4(+) memory T cells resemble the T helper type 1 (T(H)1) and interleukin 17 (IL-17)-producing T helper (T(H)17) subsets described in vitro. Intravenous or intranasal infection with Listeria monocytogenes induced pMHCII-specific CD4(+) naive T cells to proliferate and produce effector cells, about 10% of which resembled T(H)1 or T(H)17 cells, respectively. T(H)1 cells were also present among the memory cells that survived 3 months after infection, whereas T(H)17 cells disappeared. The short lifespan of T(H)17 cells was associated with small amounts of the antiapoptotic protein Bcl-2, the IL-15 receptor and the receptor CD27, and little homeostatic proliferation. These results suggest that T(H)1 cells induced by intravenous infection are more efficient at entering the memory pool than are T(H)17 cells induced by intranasal infection.

Survival of IFN-γ and IL-17A-producing 2W1S:I-Ab-specific CD4+ memory T cells. Mean number (± SD, n = 3–5 at each time point) of total 2W1S:I-Ab-specific CD4+ T cells (circles) induced by intravenous (a) or intranasal (b) infection and 2W1S:I-Ab-specific CD4+ T cells that made IFN-γ but not IL-17A (a, triangles) or IL-17A but not IFN-γ (b, squares) after challenge with LM-2W1S.

Surface phenotype of 2W1S:I-Ab-specific T cells. Representative plot of CCR7 and CD27 expression on 2W1S:I-Ab-specific T cells in mice at least 20 days after intravenous (a,b) or intranasal (c,d) infection.The quadrant lines were based on 2WIS:I-Ab− CD44low naive cells in each sample. This population was uniformly CCR7high and contained CD27low and CD27high subsets. The horizontal line was set at the lowest level of CCR7 on the entire population and the vertical line at the midpoint between the CD27low and CD27high subsets. (a) Cells that produced IFN-γ but not IL-17A (left) or neither (right) after challenge with LM-2W1S. (b) T-bet+ (left) or T-bet − (right) antigen-experienced cells without challenge (c) Cells that produced IL-17A but not IFN-γ (left) or neither (right) after challenge with LM-2W1S. (d) RORγt+ (left) or RORγt − (right) antigen-experienced cells without challenge. The values on the plots represent the mean percentage of cells (± SD, n ≥ 4) in the indicated quadrants. Data are representative of seven (a), four (b), six (c), or two independent experiments (d).

CD4+ memory T cells undergo limited homeostatic proliferation. (a) Representative BrdU histograms for total (left), CD27+ (middle), or CD27− (right) 2W1S:I-Ab+ CD4+ memory cells in mice fed BrdU for 14 days beginning 40 days after intravenous LM-2W1S infection, along with a histogram of total CD4+ T cells (gray) from a mouse that did not receive BrdU (left). Gates used to identify BrdU+ cells are shown. (b) Scatterplot of the percentage of BrdU+ 2W1S:I-Ab+ CD4+ memory T cells that were CD27+ or CD27− in individual mice, based on the gates shown in (a). (c) Representative contour plot of CD122 and CD27 on 2W1S:I-Ab+ CD4+ memory T cells induced by intravenous infection. Mean percentages (± SD, n = 5) of CD122+ cells are shown in the relevant quadrants. (d) Scatterplot of the percent BrdU+ 2W1S:I-Ab+ CD4+ memory cells in individual mice that were not injected (circles) or injected with IL-15–IL-15Rα complexes (triangles) and given BrdU for 5 days beginning 20 days after intravenous LM-2W1S infection. BrdU+ cells were identified as shown in (a). Representative histograms of BrdU incorporation by CD27+ (solid line) or CD27− (gray) 2W1S:I-Ab+ CD4+ memory T cells in mice that were not injected (left) or injected with IL-15–IL-15Rα complexes (right) and given BrdU for 5 days beginning 20 d after intravenous LM-2W1S infection. Horizontal bars on each scatter plot indicate the means for each population. The number of BrdU+ cells in the IL-15–IL-15Rα complex-treated group was significantly greater than in the untreated group (asterisk, P = 0.003). Data are representative of three (a,b), two (c), one experiment (d).